The present invention relates to systems and methods for accurate positioning of tools, fasteners and implants within a patient. More particularly, the invention relates to orthopaedic surgical procedures requiring accurate shaping of the bone or placement of bone engaging elements.
Damage or disease can deteriorate the bones, articular cartilage and ligaments of human joints, such as the knee, which can ultimately affect the ability of the natural joint to function properly. To address these conditions, prosthetic joints have been developed that are mounted to prepared ends of the bones of the joint, namely the tibia and femur in the case of a knee prosthesis.
The implant components define interior mounting surfaces that often require involved cuts into the bone, such as the distal end of the femur or the proximal end of the tibia. The implant components are selected to restore or emulate as much of the natural motion of the knee joint as possible. Consequently, implant positioning with respect to the natural bone is critical. For instance, a proper implant will maintain the proper tension in the retained ligaments supporting the joint.
Preparation of the natural joint to receive a prosthesis must be painstaking to ensure the properly selected implant will work for its intended purpose. For instance, in preparing a knee joint to receive a prosthesis, the orthopaedic surgeon typically uses templates to determine the proper size of the implant components. The surgeon may also measure the joint gap and choose a spacer that can be used in the procedure to maintain that gap. Since the femoral component of the knee prosthesis requires complex cuts in the femur, a femoral resection guide is used, such as the resection guide 10 shown in FIG. 1. A saw guide 12 is aligned with the end of the femur F with its guide slot 14 oriented to make the proper cut in the bone. The saw guide is supported on the bone by a mounting block 16 that is fastened to the distal end of the femur F by a pair of mounting pins 17. The orientation of the saw guide 12 is adjusted by controlling an adjustment knob 19 and sliding an adjustment rod 18.
While the vertical position of the saw guide slot 14 is adjusted by sliding the adjustment rod 18 relative to the mounting block 16, the angular orientation of the saw guide is determined by the placement of the mounting pins 17 supporting the mounting block. It can be appreciated, then, that the placement of the mounting pins 17 must be as accurate as possible to ensure a proper cut. In order to account for the potential for error in initial placement of the pins, more complex cutting guide assemblies have been developed. These complex devices include multiple degree-of-freedom fine tuning adjustments that can be “dialed in” to optimize the orientation of the saw guide. While accurate bone cuts can be made with these complex devices, they are naturally more expensive and require greater maintenance than cutting blocks as simple as or more simple than the assembly 10 of FIG. 1.
Many orthopaedic procedures require performing operations on only partially exposed bones and joints. The use of an imaging modality such as intraoperative x-rays or CT scans can open the surgeon's “field of vision” without requiring greater tissue exposure of the patient. Image guided surgical techniques have been used in orthopaedic surgeries, as well as many other types of surgeries where the surgical site is difficult to view directly.
An example of an image guided surgery (IGS) system is shown in FIG. 2. An x-ray imaging apparatus 27 is situated adjacent the operating table 25 to provide an intraoperative view of the surgical site, in this case the femur F. An x-ray monitoring apparatus 28 provides means for viewing the x-ray scan as the femur is being prepared to receive an implant, for instance. The IGS system also includes a localizer apparatus 29 that provides means for determining the position of elements in the surgical arena. The apparatus 29 includes a localizing device or sensor 31 that feeds information to a processor or computer 33 for display on a monitor 35. The localizing device 31 can take on a variety of forms, but all geared toward receiving signals from an emitter or position tracking element associated with a part of the patient, such as femur, or a surgical component, such as a drill guide 38. For instance, the localizing device 31 can constitute part of a visible light, IR, electromagnetic or RF triangulation system capable of fixing a position in space. Triangulation data from the localizing device 31 is fed to software within the processor that can calculate position information and generate a visual image on the display 35. Further details of suitable IGS systems can be found in U.S. Pat. No. 6,697,664, the disclosure of which is incorporated herein by reference.
As the disclosure of the '664 patent reveals, the typical image guided surgery system is complex and requires a great deal of equipment to provide real-time simulation and graphic display of the surgical site. What is needed is a system that allows for accurate bone resection or placement of surgical components without the expense and complexity of prior IGS systems.